1. Field of the Invention
This specification relates to a connecting device for control terminals in a withdrawable type circuit breaker, and more particularly, a connecting device for control terminals in a withdrawable type circuit breaker, capable of automatically connecting or separating control power source terminals for controlling the circuit breaker upon pulling out or inserting a breaker main body.
2. Background of the Invention
In general, a circuit breaker is an electrical device that opens or closes a load in a transmission, a substation or an electrical circuit, or breaks a circuit when an accident such as a ground or short circuit occurs. Among these circuit breakers, an air circuit breaker is a circuit breaker using air as an arc-extinguishing medium and is mainly used for low voltage appliances.
The circuit breakers are classified into a fixed type which is fixed in the switchboard or other places, and a withdrawable type in which a breaker main body is installed in a cradle to be pushed in or pulled out of the cradle. The withdrawable type is widely used in terms of advantageous maintenance of the breaker main body.
Meanwhile, the circuit breaker is provided with control terminals for monitoring or controlling the circuit breaker. The control terminals of the withdrawable type circuit breaker are provided in the breaker main body and the cradle. When the breaker main body is pushed into the cradle, the control terminals may be connected to each other and a control signal can be transmitted accordingly.
The withdrawable type circuit breaker is located (disposed), according to relative positions of the breaker main body and the cradle, in three positions (states), namely, a disconnect position (state) in which a control power source is completely disconnected from the cradle, a test position (state) in which the breaker main body is inserted into the cradle by a predetermined distance (depth) such that the control (power source) terminals are connected so as to check a connected state of the circuit breaker, and a connect position (state) in which the breaker main body is completely pushed into the cradle and thus main circuit terminals are connected such that a current flows along a main circuit.
Here, the control terminals are disconnected from each other in the disconnect state and connected to each other in the test state and the connect state. That is, when the breaker main body is moved from the disconnect state to the test state, a cradle-side control terminal module is fixed and a main body-side control terminal module should be moved to be connected to the fixed cradle-side control terminal module. When the breaker main body is moved from the test state to the connect state, the cradle-side control terminal module and the main body-side control terminal module should be moved together with the breaker main body while being connected to each other. Also, a disconnection process is reverse to the connection process.
Hereinafter, description will be given of a prior art (Korean Patent Application No. 10-2016-0017463 ‘Connecting device for control terminals in withdrawable air circuit breaker’ that the inventor of the present application has applied as an invention proposed for allowing connection and movement of the control terminals to be automatically executed according to a moved position of a breaker main body.
FIGS. 1 to 3 illustrate operation views of the connecting device for the control terminals in the withdrawable air circuit breaker according to the prior art, which illustrate a disconnect state, a test state and a connect state, respectively.
In the prior art, a connecting device for control terminals in a withdrawable air circuit breaker includes a fixed control terminal module 230 installed on the breaker main body 200, a movable control terminal module 130 movably installed on the cradle 100, and a locking device 400. The locking device 400 operates in cooperation with a transfer unit.
The transfer unit includes a screw shaft 310 rotated by a handle (not illustrated), a rack 320 moving back and forth in response to the rotation of the screw shaft 310, a pinion 330 engaged with the rack 320, a link assembly 340 coupled to the pinion 330, and a cam 350 coupled to the link assembly 340.
When the breaker main body 200 is pushed into the cradle 100 and moves from the disconnect state to the test state (FIG. 1→FIG. 2), the rotation of the screw shaft 310 is transferred to the rack 320, the pinion 330, the link assembly 340 and the cam 350 and thus the cam 350 is rotated in a counterclockwise direction. The locking device 400 is restrained at a head portion of the cam 350 so as to lock the movable control terminal module 130. In this instance, a locking part 413 formed at the upper end of the locking device 400 is in a state of restraining a support member 132 of the movable control terminal module 130. Accordingly, the fixed control terminal module 230 of the breaker main body 200 is inserted into the movable control terminal module 130 and connected to a control circuit.
When the breaker main body 200 is continuously inserted into the cradle 100 from the test state to the connect state (FIG. 2→FIG. 3), the cam 350 is further rotated such that the head portion of the cam 350 pulls down the locking device 400. Accordingly, the locked movable control terminal module 130 is released, and thus the control terminal modules 130 and 230 are moved up to the connect state while being connected to each other.
However, in the prior art, since the locking device 400 operates in cooperation with the transfer unit, it is dependent on the transfer unit. That is, the locking device 400 may be likely to be malfunctioned due to an error of the transfer unit, and a mechanism that operates in cooperation with the transfer unit should be designed. As a result, the construction of the locking device 400 becomes complicated and instability and inaccuracy may occur in the operation of the locking device 400. Accordingly, there is a need for a locking device that independently operates without the cooperation with the transfer unit.